1. Field of the Invention
The present invention relates generally to electrical receptacles and more specifically to a high grade electrical receptacle utilizing terminals fabricated from ordinary brass.
2. Description of the Prior Art
High grade electrical receptacles are specially designed electrical receptacles that are used in hospitals or that meet demanding federal specifications. High grade electrical receptacles are generally similar to ordinary residential use electrical receptacles except that the terminals are fabricated from high strength copper alloys instead of ordinary copper alloys such as 70/30 (70% copper, 30% zinc) cartridge brass. For example, a manufacturer of electrical receptacles may have to use CDA (Copper Development Association's) No. 688 copper alloy instead of ordinary 70/30 cartridge copper to make a high grade receptacle which will pass U.L. (Underwriters Laboratories) Standards or Federal specification standards.
CDA No. 688 alloy is a relatively expensive copper alloy which has a tensile strength of 109 kips and an IACS conductivity of 18%. On the other hand, 70/30 cartridge brass is relatively inexpensive, has a better conductivity of 28%, but a lower tensile strength of 76 kips Manufacturers must use the higher strength alloys such as CDA No. 688, because terminals made of lower strength alloys, such as cartridge brass can become overstressed and will fail to secure adequately an electrical plug which is inserted therein. Such a failure is intolerable in a hospital emergency room or other demanding location.
Federal specifications require testing to determine whether an electrical receptacle can be considered a high grade receptacle. The test consists of taking a maximum thickness electrical plug blade having a thickness of 0.075" and inserting it into the electrical receptacle twenty times. A minimum thickness electrical plug blade having a thickness of 0.055" is then attached to a weight of 1.5 pounds and is inserted into the electrical receptacle. The electrical receptacle is held in a horizontal position face down with the 1.5 pound weight suspended in mid-air. The electrical receptacle must hold the weight for at least one minute for the electrical receptacle to pass federal specification requirements.
Prior art electrical receptacles having their terminals fabricated from ordinary copper alloys, such as cartridge brass, cannot pass the U.L. test, since the terminals become overstressed when the thick 0.075" blade is repeatedly inserted into the terminals. Accordingly, a novel design high grade electrical receptacle having its terminals fabricated from a relatively low strength copper alloy would have a decreased cost and improved conductivity.